package list;

public class LinkedList<E> {
    private class Node{
        public E e;
        public Node next;

        public Node(E e, Node next) {
            this.e = e;
            this.next = next;
        }

        public Node(E e) {
            this(e,null);
        }

        public Node() {
            this(null,null);
        }

        @Override
        public String toString() {
            return e.toString();
        }
    }

    // 虚拟头结点，让所有的节点都有前一个节点。没有特殊节点。
    private Node dummyHead;
    private int size;

    public LinkedList() {
        dummyHead = new Node(null,null);
        size = 0;
    }

    public int getSize(){
        return size;
    }

    public boolean isEmpty(){
        return size == 0;
    }

    public void add(int index, E e){
        if(index < 0 || index > size){
            throw new IllegalArgumentException("");
        }

        Node prev = dummyHead;
        for (int i = 0; i < index; i++) {
            prev = prev.next;
        }
//            Node node = new Node(e);
//            node.next = prev.next;
//            prev.next = node;
        prev.next = new Node(e,prev.next);
        size++;
    }
    // 链表头加数据
    public void addFirst(E e){
        add(0,e);
    }

    public void addLast(E e){
        add(size,e);
    }

    public E get(int index){
        if(index < 0 || index >= size){
            throw new IllegalArgumentException("illegal index!");
        }
        Node cur = dummyHead.next;
        for (int i = 0; i < index; i++) {
            cur = cur.next;
        }
        return cur.e;
    }

    public E getFirst(){
        return get(0);
    }

    public E getLast(){
        return get(size - 1);
    }

    public void set(int index, E e){
        if(index < 0 || index >= size){
            throw new IllegalArgumentException("");
        }
        Node cur = dummyHead.next;
        for (int i = 0; i < index; i++) {
            cur = cur.next;
        }
        cur.e = e;
    }

    public boolean contains(E e){
        Node cur = dummyHead.next;
        while(cur != null){
            if(cur.e.equals(e)){
                return  true;
            }
            cur = cur.next;
        }
        return  false;
    }

    public E remove(int index){
        Node prev = dummyHead;
        for (int i = 0; i < index; i++) {
            prev = prev.next;
        }
        Node retNode = prev.next;
        prev.next = retNode.next;
        retNode.next = null;
        size--;
        return retNode.e;
    }

    public E removeFirst(){
       return remove(0);
    }

    public E removeLast(){
        return remove(size - 1);
    }

    public void removeElement(E e){

        Node prev = dummyHead;
        while(prev.next != null){
            if(prev.next.e.equals(e))
                break;
            prev = prev.next;
        }

        if(prev.next != null){
            Node delNode = prev.next;
            prev.next = delNode.next;
            delNode.next = null;
            size --;
        }
    }
    @Override
    public String toString() {
        StringBuilder res = new StringBuilder();
        Node cur = dummyHead.next;
        while(cur!=null){
            res.append(cur + "->");
            cur = cur.next;
        }
        res.append("NULL");
        return res.toString();
    }
}
